Cu2+ inhibitionofgelsecretioninthexylemandits potentialimplicationsforwateruptakeofcutAcacia holosericeastems

Abstract

Maintaining a high rate of water uptake is crucial for maximum longevity of cut stems. Physiological gel/tylosis formation decreases water transport efficiency in the xylem. The primary mechanism of action for post-harvest Cu2+ treatments in improving cut flower and foliage longevity has been elusive. The effect of Cu2+ on wound-induced xylem vessel occlusion was investigated for Acacia holosericeaA. Cunn. ex G. Don. Experiments were conducted using a Cu2+ pulse (5 h, 2.2 mM)andaCu2+ vase solution (0.5 mM) vs a deionized water (DIW) control. Development of xylem blockage in the stem-end region 10 mm proximal to the wounded stem surface was examinedover21daysbylightandtransmissionelectronmicroscopy.Xylem vesselsofstemsstoodintoDIWwereoccludedwithgelssecretedintovessel lumens via pits from surrounding axial parenchyma cells. Gel secretion was initiated within 1–2 days post-wounding and gels were detected in the xylem from day 3. In contrast, Cu2+ treatments disrupted the surrounding parenchymacells,therebyinhibitinggelsecretionandmaintainingthevessel lumens devoid of occlusions. The Cu2+ treatments significantly improved wateruptakebythecutstems ascomparedto thecontrol.